Milwaukee Metropolitan Sewerage District

US - To Mitigate Flooding, States and Communities Increasingly Turn to Nature

Wetlands, marshes, and other natural features can reduce risk and save money

As many around the U.S. mark the 51st Earth Day, communities and states are increasingly recognizing that smart conservation can help people as well as the natural world. One example of this is the growing adoption of nature-based solutions to mitigate flooding. Such strategies include replacing impervious surfaces such as asphalt with gravel to allow rainwater to seep into the ground, converting developed areas in flood plains to open green space to absorb floodwaters, and preserving and restoring “living shorelines”—dunes, wetlands, mangrove forests, and other natural features—which diffuse rising waters and help blunt the force of storm-driven waves.

In many cases, such “green” and “blue” infrastructure reduces long-term operations and maintenance costs for local and state governments compared with levees, dams, floodgates, and other hard infrastructure. In one example, research shows that living shorelines are often more cost-effective than traditional shoreline armoring, such as bulkheads and seawalls, in protecting communities from flooding.

Flood-related disasters are the costliest in the U.S., accounting for more than $900 billion in damage and economic losses—across all 50 states—since 2000. In response, community leaders and policymakers are developing an array of projects, policies, and financial incentives to harness the power of nature to manage floodwaters.

For example, in the 1990s, as Milwaukee experienced population growth, increased development, and more frequent climate impacts, its leaders developed an innovative approach to combat repeated floods. The Milwaukee Metropolitan Sewerage District (MMSD) began removing much of the concrete lining from local streams and rivers that had been installed decades earlier, which exacerbated poor stormwater runoff conditions, and replaced it with natural materials.

MMSD spent $120 million to restore Lincoln Creek, a 9-mile waterway in a densely populated section of Milwaukee that had flooded more than 4,000 times since the lining was installed. A combination of grass, rocks, and native vegetation replaced the concrete, and today the creek is less likely to spill over its banks during heavy rainfalls, all while the natural buffers provide habitat for wildlife.

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